Heater



FIG. 1 is a right, front, top perspective view of a heater in accordance with the present invention;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a left-side elevation view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The broken lines illustrate portions of the heater that form no part of the claimed design. 

CLAIM The ornamental design for a heater, as shown and described. 